Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Fast dissemination of GRB afterglow information Patrizia Ferrero (IASF-BO, OACT & Universita’ di Teramo)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Our collaboration Patrizia Ferrero (IASF-BO, OACT & Universita’ di Teramo) Corrado Bartolini, Adriano Guarnieri, Adalberto Piccioni (Universita’ di Bologna) Graziella Pizzichini (IASF-BO)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, The GRB Coordinates Network (GCN)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3,  The GCN was originally developed at NASA/MSFC as BACODINE under Scott Barthelmy to support BATSE positions/identifications  Now at NASA/GSFC, still under Scott Barthelmy, it distributes near real time GRB positions from active satellites as well as reports of follow-up observations by ground based observers 

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Why are GCN Circulars so important to us? They give us information about the OT (optical transient):  localization and position  magnitude  the time of the optical decay essential data to plan other observations.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, But are GCN data always so complete, exhaustive and precise? The answer is: they aren’t!! We have to remember that they are preliminary data, that it is not mandatory for observers to issue a GCN as soon as they obtain data and that issued data are no longer private, but public.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, In some cases data are abundant in different filters, in other cases they are relatively scarce. The quality and the quantity of the GCN data are determined by several factors, which could be summarized in this way:

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3,  OT features  Filters  Number of observations  Calibrations

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, OT features, Filters and Number of observations The situation is different for  GRB with optical afterglow  GRB without optical afterglow

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, OT features, Filters and Number of observations: GRB with OT The kind of optical afterglow would be fundamental for the choice of filter and the amount of observations. bright OT with a slow decay different filters (B,V,Rc,Ic) a lot of observations

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, OT features, Filters and Number of observations: GRB with OT bright OT with a rapid decay different filters (B,V,Rc,Ic) few data faint OT Rc and Ic filters few observations

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB021004: light curves in several filters (data from GCN)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB030226: light curves in different filters (data from GCN) A rapid decay could explain the lack of more optical data.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, A lot of multiband data could be useful: to trace the GRB light curves to locate on them the point of break to analyse the color indices and to confirm the studies of them made by Simon et al

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, OT features, Filters and Number of observations: GRB without OT In the case of GRB without detected optical afterglow, we have usually upper limits (sometimes in different bands) and few observations. An example.....

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB030416: upper limits in different filters (data from GCN) Here, in spite of the lack of the OT, the observers attempted to give magnitude limits in four filters.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Calibrations When a GRB event occurs, all of us are wainting for Henden’s precise photometry to calibrate our data. However, at least at the beginning of data release, we must do without it and choice a system which to refer to. USNOA.2, USNOB.1 or something else?

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, The Guide Star Catalog - II The GSC2.2 is an all-sky catalog based on 1” resolution scans of the photographic Sky Survey plates, at two epochs and three bandpasses, from the Palomar and UK Schmidt telescopes (DSS). The GSC2.2 is a joint project of the Space Telescope Science Institute and the Osservatorio Astronomico di Torino.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GSC 2.2 vs USNO-B USNO-A2.0USNO-B1.0GSC 2.2 Total Object 526,230,8811,042,618,261455,851,237 Magnitude Limit O=21 E=20 V=21 F=18.5 J=19.5 V=19.5 Astrometry Errors 0.25”0.2”0.3” Photometry Errors mag0.3 mag mag In the future: GSC-2.3 with 997,028,547 objects and mag limit F<20.5 & J<22.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB021004: Rc light curves with different calibrations (data from GCN)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB030329: Rc light curves with different calibrations (data from GCN)

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, In other cases it is a matter of bad luck. For example....

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, GRB030328: light curves of the “orphan” GRB (data from GCN) Although it had about Rc=18, when it was localized, we have few optical data because it was “obscured” by the famous GRB

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Conclusions Our conclusions are fairly simple and could be easily anticipated. It would be very helpful and productive, in order to obtain the best set of data:  to have, at least, early estimates of OT magnitudes in several filters,  to converge as soon as possible on the same calibration system or to define some precise rules in order to choice it,  to plan and to share the task of following the OTs with multifilter photometry between different observatories.

Patrizia Ferrero 3rd Integral Bart Work Shop Chocerady - November 1-3, Thank You for Thank You forYour Attention !!! Attention !!!